1. Field of Invention
This invention relates to a tunable optical routing device.
2. Description of the Related Art
Optical communications networks that use wavelength division multiplexing (WDM) require optical routing devices, or add/drop devices, to select one or more wavelength channels from a multiple wavelength channel signal and provide the selected wavelength channel(s) to a subscriber. The add/drop devices also add one or more wavelength channels received from a subscriber to the multiple wavelength channel signal. Thus, a subscriber can receive from an add/drop device a particular wavelength channel and the information contained in the channel, e.g., telephone voice information, add communication information to the channel, and send the channel back to the add/drop device so that the added communication information can be transmitted to another party.
Current add/drop devices are either only capable of adding or dropping a single fixed wavelength channel, or adding or dropping a fixed set of multiple wavelength channels. Devices capable of adding or dropping a fixed set of multiple wavelength channels are not capable of adding or dropping the multiple channels using a single add or drop port, and must instead use multiple add or drop ports, one port for each wavelength channel. In addition, current add/drop devices cannot be tuned to select different sets of wavelength channels. That is, current devices can only select a single fixed channel or a fixed set of channels. Re-tuning of the devices requires that filters or other components of the devices be replaced so that another or additional channels can be added or dropped.